An electron beam device such as a scanning electron microscope (SEM) used for observing, inspecting, and measuring a sample with an electron beam irradiates the sample by accelerating electrons emitted from an electron source and converging the electrons on the sample surface by an electrostatic lens or an electromagnetic lens. Such electrons are referred to as primary electrons. Secondary electrons (electrons of low energies are referred to as secondary electrons and electrons of high energies are referred to as backscattered electrons dividedly in some cases) are emitted from the sample by the incidence of the primary electrons. A scanning image of a fine pattern and a composition distribution of the surface of a sample can be obtained by detecting such secondary electrons while an electron beam is deflected and scans the surface of the sample. Further, an absorbed current image can also be formed by detecting electrons absorbed in a sample.
In scanning electron microscopy, it is necessary to increase the amperage of an electron beam and thus increase a signal amount for observing the bottom of a deep groove or a deep hole or measuring high-precision pattern dimensions. Moreover, unless an aperture angle of an electron beam is reduced, a beam blur caused by a defocus increases and it comes to be difficult to observe the bottom of a deep groove or a deep hole separately from the upper part. If an aperture angle is reduced while an amperage is maintained, an electron source image glows large and a resolution lowers.
Because of this, a method for improving the resolution of an image obtained by image processing is known. A method of estimating the size and the profile of a primary beam and processing an image by using Fourier transformation on the basis of the estimation is disclosed in Patent Literature 1 and Patent Literature 2.